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A position sensorless control method for PM synchronous motors is proposed in this paper. It relies on the magnetic saliencies to estimate the position of the rotor. In usual sensorless methods, a signal is injected in the αβ or dq components. In the proposed method, the signal is injected in the zero-sequence component. The high-frequency inherent zero-sequence component produced by a space-vector pulsewidth modulator (PWM) is used. In this way, no modification is required in the PWM, even at zero voltage, and the injected signal does not interact with the current controller. The response to the injected signal is obtained by a simple current derivative sensor. With this method, the position can be evaluated with high dynamics and with a high signal-to-noise ratio. The performance of the proposed method is evaluated with an experimental setup, using standard industrial servomotors with surface-mounted magnets.
Date of Publication: Dec. 2011